In a fiber optic gyroscope, polarization errors result from interference between the primary lightwaves and spurious lightwaves, as well as interference among spurious lightwaves. The weak spurious lightwaves come from polarization cross-couplings at non-ideal fiber splices, in birefringent coil fiber, at junctions between integrated optical circuit (IOC) waveguides and its pigtail fibers, and inside optical components. These spurious lightwaves reaching the photodetector carry erroneous Sagnac phase information because they traveled nonreciprocal paths in the sensing loop. Methods of using Lyot-type fiber depolarizers and tailoring of the depolarizer polarization maintaining (PM) fiber lengths have been suggested to mitigate polarization errors. In prior art polarization error models, the polarization errors are evaluated in the time domain by keeping track of time and phase delays of spurious lightwaves originating from cross-couplings in the optical circuit. Wavelength dependent properties of the optical component, such as polarization dependent loss (PDL), polarization mode dispersion (PMD), etc., are often completely or partially ignored in the model. Specifically, for a depolarized gyroscope using a non-polarization maintaining single-mode (SM) fiber coil, the impact of the SM coil birefringence on the polarization error is empirically taken into account by assuming a broadened light source coherence function. Such simplifications lead to inaccuracies (up to one order of magnitude of deviation) in evaluation of polarization errors. More accurate modeling methods are needed to find optimal design parameters of interferometric fiber optic gyroscopes with reduced polarization error and bias instability.